Save your /etc/X11/xorg.conf somewhere and then replace it by the new one I gave you: sudo cp your-new-file.txt /etc/X11/xorg.conf

Note: if you don't want a English keyboard, edit this file (sudo gedit /etc/X11/xorg.conf), find the line

Option "XkbLayout" "en"

and replace "en" by "de" if you have a German keyboard, "fr" if you have a French keyboard, "it" if you have an Italian keyboard, etc.

Reboot or restart the X server and 3D acceleration should be activated. glxinfo | grep rendering will tell you if direct rendering is activated or not.

If you want to configure your driver by yourself, also install fglrx-control and run sudo fglrxconfig. It will create a new /etc/X11/xorg.conf. Before rebooting, you must edit it and add your resolution (1280x800) which is not given by default by ATI. The Subsection "Display" should look like this: